Asphalt roofing element



June 25, 1963 w. G. CRAIG 3,095,339

ASPHALT ROOFING ELEMENT Filed March 25, 1958 INVENTOR.

WILLIS G. CRAIG AT TORNEYS United States Patent ,0

Ohio

Filed Mar. 25, 1958, Ser. No. 723,903 4 Claims. (Cl. 154-51) This invention relates as indicated to a roofing element. More particularly itrelates to an asphaltic roofing element which is useful in prolonging the life of a built-up roof surface. It is useful not only in the preparation of new roof surfaces, but also in the repair of old, worn roof surfaces.

The roof surfaces of many buildings, particularly commercial and industrial buildings, consist of flat slabs of concrete, metal, wood, etc. as the principal supporting structure. These supporting slabs are covered in most instances with asphalt-saturated felts to give the roofing a uniform protective coating. The asphalt-saturated felt serves not only to seal the joints between the abutting concrete slabs, but also to eliminate the crevices of these joints and to provide a smooth surface which will prevent the collection of water from rain and snow.

As the supporting slabs are not fastened either to each other or to their supporting understructure, but merely rest in their positions, it is apparent that they will shift their positions from time to time with any shifting of the building structure which they cover. It is apparent furtherrnore that such shifting of these supporting slabs will not be uniform, but that some will shift more than others. Such motion of the slabs will place a considerable stress upon that portion of the asphaltic layer immediately above the joints between any pair of slabs, This stress inevitably results in the rupture of the asphaltic surface immediately above these joints with the result that protection from the elements ofweather is no longer provided by the asphaltic layer. I

It is an object of the present invention to provide an improved asphaltic roof surface.

Another object of the present invention is to provide a roofing element which serves as an effective seal of cracks in a roof surface.

Other objects of the invention will become apparent from the following description thereof.

An effective means has been discovered whereby an asphaltic surface can be strengthened along the lines of joints between supporting slabs of the surface, Which consists of a roofing element comprising in combination a first strip of porous, asphalt-bonded fibrous mat 4 to 12 inches wide, and centered longitudinally thereunder and in facewise contact therewith a second, asphalt-impermeable strip narrower than said first strip and held in place by the surface tack of said first strip, said second strip being characterized by a tensile strength less than that of said first strip and an adhesion to asphalt less than the cohesion of asphalt.

The porous asphalt-bonded fibrous mat is preferably a glass fibrous mat, and a particularly suitable asphaltbonded glass fibrous mat is described in U.S. 2,811,769. Such a mat may be prepared by spraying hot discrete asphalt particles upon a water-felted mat of chopped glass strands. A mat prepared in this manner is characterized by its great strength and light weight, and also by its relatively high concentration of asphalt with respect to its glass content. Other asphalt-bonded mats may also 'be used with success; thus an asphalt-bonded Saran fiber mat is useful, so is an asphaltic mat prepared with chopped nylon strands, cot-ton, jute, Orlon, etc. and many other synthetic fibers can be used in the preparation of mats for the purposes of this invention.

Ordinarily this first porous strip should be about 4 inches wide. This size is ideal for use in preparing new roof surfaces and also is quite applicable in repairing worn roofing surfaces. In some cases a worn roof surface, however, may have sufficiently wide cracks in its surface as to require the use of a wider first strip and in some severe cases a strip 12 inches in width will be most useful.

The second strip, an asphalt-impermeable strip, narrower than the first, asphalt-bonded strip, must have a tensile strength less than that of the asphalt-bonded strip. The reason for this limitation upon the strength of the second strip is associated with its function in distributing the stresses on the upper first strip (occasioned by the shifting of the supporting slabs of the roof surface) about a wider area than that immediately over the joints between these supporting slabs.

To illustrate the invention, an asphalt-impermeable strip about 2 inches in width is placed along the joint between abutting concrete slaps of a roof surface and centered thereon. Immediately above this 2-incl1 wide strip there is placed a 4-inch wide strip of a porous alphalt-bonded glass fibrous mat. This second, asphaltic mat is centered atop the lower, narrower strip so as to overlap on each side of this narrower strip. Then the overlapping edges of the upper strip are anchored to the supporting concrete slabs by mopping a clay asphalt emulsion on to the surface of this upper strip. The asphalt-emulsion impregn-ates the pores of this upper strip making contact with the concrete slabs underneath the overlapping edges and dries to leave an effective seal between the concrete and the overlapping portions of the asphalt-bonded glass mat.

The second, flexible, narrower strip, being asphaltimperrneable, prevents attachment of the center portion of the upper strip corresponding to the area of the underneath strip to the supporting roof structure. Because of this and also because it is weaker in terms of tensile strength than the upper first strip it allows the stresses caused by any shifting of the abutting supporting slabs to be distributed throughout the upper asphaltic strip about an area defined by the width of the lower, asphaltimpermeable strip.

The invention may be illustrated further by reference to the figurwof the drawing. FIGURE 1 is a top View of the combination of strips placed over the joint of two abutting panels of a roof surface. The uppermost strip is defined by 5, 6, 7 and 8. The narrower, asphalt-impermeable strip which lies immediately beneath the wider upper, asphaltic strip is represented by 13 and 14- and the width of the lower asphalt-impermeable strip is indicated by 11 and 12. The abutting panels are 15 and 16.

An important consideration in the selection of materials that can serve as the lower, narrower asphalt-impermeable stripis that this material must be one which is free to move either with respect to the supporting roof surface itself or with respect to the upper asphaltic strip. It is apparent that this condition must exist if the stresses caused by the movement of the supporting slabs are to be distributed about an area wider that that of the joint being covered. In some special circumstances this narrower, asphalt-impermeable strip may be such that it adheres neither to the supporting roof structure nor to the covering asphaltic mat. Ordinarily, however, this narrower strip will be adherent to one of these surface, and more usually this narrower strip will adhere to the covering asphaltic strip.

A particularly suitable material for use as this narrower asphalt-impermeable strip is tissue paper which has been coated on one side with a thin film of polyethylene. The polyethylene film serves to prevent adhesion of the strip to the asphalt of old, worn roof surfaces, and also to pre- 3 vent the combined strips from sticking to itself when it is rolled for storage purposes. Other materials which have been used with success as the asphalt-impermeable strip include tissue paper alone (for use on new roof surfaces), Saran (a copolymer of 95% vinylidene chloride and 5% vinyl chloride), aluminum foil, cellophane, and -pound kraft paper.

Still other materials which have been used successfully include synthetic resins which are painted over the joint between abutting surfaces. These include polyvinyl alcohol, polyvinyl chloride, various vinyl chloride copolymers, polyvinyl acetate, GRS-type copolymers and the like. The use of such materials as this narrower, underlying strip illustrates the situation in which this strip adheres to the supporting roof structure, but is free to move with respect to the upper asphaltic strip. In this situation the asphalt-impermeable strip is sufficiently flexible to move with any movement of the abutting slabs of the roof. Being non-adherent with the asphaltic strip above, this movement does not transmit any stresses to the asphaltic strip.

With respect to the situation in which the asphalt-impermeable strip adheres to the upper asphaltic strip, but does not adhere to the supporting roof structure, any movement of the abutting slabs of this roof does not transmit stresses to either of the strips which overlie the slabs because the narrower, asphalt-impermeable strip is independent of any such motion.

As mentioned earlier the lower, asphalt-impermeable strip must have a tensile strength less than that of the upper, asphaltic strip. If this is not the case the lower strip will act to reinforce the upper strip and any stresses imposed upon the system will cause the upper strip to rupture along the lines which correspond to the edges of the lower reinforcing strip. It is apparent therefore that the lower strip must have a sufficiently low tensile strength that it does not act to reinforce the upper strip.

The lower, asphaltic-impermeable strip should also be characterized by an adhesion to asphalt less than the cohesion of asphalt. This property enables the lower strip to become detached from the upper asphaltie strip or an asphaltic roof surface when stresses are applied to the system. A specific illustration of the invention is as follows: A 2-inch wide strip of polyethylene-coated tissue paper is placed (polyethylene side face down) atop the joint formed by abutting concrete slabs of a new roof. Immediately on top of this strip there is placed a 4-inch wide stripof an asphalt-bonded, glass fibrous mat (prepared as in US. 2,811,769) such that a 1-inch selvage overlies each edge of the lower strip. An aqueous clay asphalt emulsion containing 48% asphalt and 2% clay is mopped on to the top layer until the pores thereof are thoroughly saturated. When the emulsion has dried the overall roof then may be surfaced by any of the methods well known in the art.

It is apparent that the upper, asphaltic strip, being anchored to separate supporting slabs which are free to move with respect to each other, must be capable of elongation. Likewise of course the anchoring substance (the residue from the clay asphalt emulsion of the above illustration) should also have this property. For the purposes of this invention it is necessary that this upper, asphaltic strip, when anchored to a roof surface, be characterized by an elongation of at least 10% before rupture.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent of such be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A roofing clement comprising in combination a first strip of porous, tacky asphalt-bonded fibrous mat 4 to 12 inches wide, and centered longitudinally thereunder and held in facewise contact therewith by the surface tack of said first strip, a second, asphalt-impermeable strip narrower than said first strip, said second strip being characterized by a tensile strength less than that of said first strip and an adhesion to asphalt less than the cohesion of asphalt.

2. The roofing element of claim 1 characterized further in that the first strip of porous, asphalt-bonded fibrous mat is an asphalt-bonded glass fibrous mat.

3. The roofing element of claim 1 characterized further in that the first strip of porous, asphalt-bonded fibrous mat is an asphalt-bonded mat of chopped glass fiber strands.

4. The roofing element of claim 1 characterized further in that the second, asphalt-impermeable strip is a synthetic resin.

References Cited in the file of this patent UNITED STATES PATENTS 1,227,520 A-ngier May 22, 1917 1,637,480 Gage Aug. 2, 1927 1,642,282 Weiss Sept. 13, 1927 1,694,523 White Dec. 11, 1928 1,751,327 Haire Mar. 18, 1930 2,078,049 Benedict Apr. 20, 1937 2,133,183 Baird Oct. 11, 1938 2,314,523 \Speer Mar. 23, 1943 2,315,851 Goldman Apr. 6, 1943 2,550,465 Gorski Apr. 24, 1951 2,624,683 Bezman Jan. 6, 1953 2,811,769 Craig Nov. 5, 1957 2,863,405 Lei'brook Dec. 9, 1958 2,962,405 Mortland Nov. 29, 1960 OTHER REFERENCES Engineering News Record, Feb. 17, 1938, page 272.

American Roofer, December 1946, pages 12, 13, and 25-27, inclusive.

Addex publication RP. -28pa by Labco of Cleveland 6, Ohio, pages 1 and 2, Jan. 15, 1957. 

1. A ROOFING ELEMENT COMPRISING IN COMBINATION A FIRST STRIP OF POROUS, TACKY ASPHALT-BONDED FIBROUS MAT 4 TO 12 INCHES WIDE, AND CENTERED LONGITUDINALLY THEREUNDER AND HELD IN FACEWISE CONTACT THEREWITH BY THE SURFACE TACK OF SAID FIRST STRIP, A SECOND, ASPHALT-IMPERMEABLE STRIP NARROWER THAN SAID FIRST STRIP, SAID SECOND STRIP BEING CHARACTERIZED BY A TENSILE STRENGTH LESS THAN THAT OF SAID FIRST STRIP AND AN ADHENSION TO ASHPALT LESS THAN THE COHENSION OF ASPHALT. 